There has been controversy in the past week about the sentences served by convicted criminals following two-high profile cases involving jail terms for paedophiles.

Why are these cases in the news?

Craig Sweeney abducted and sexually abused a girl aged three. He was sentenced to life - with the judge giving him an 18-year sentence - but will be eligible to be considered for parole in five years.

A separate case saw the Court of Appeal dealing with the case of Alan Webster, who had raped a baby. It increased the minimum tariff on his life sentence so he would be not eligible to be considered for parole for eight years, rather than the six years stated previously.

Since the Sweeney case - and the disclosure that 53 other "lifers" have been freed after serving less than six years - the Home Office has faced intense scrutiny over the handling of such prisoners.

Why doesn't life mean life?

In these cases the reason the minimum tariff is low is because - under the guidelines - judges should reduce a sentence by a third if there is an early admission of guilt (this is in order to incentivise guilty pleas to save time, costs and victims having to testify).

In addition, offenders are eligible to be considered halfway through their sentence.

However, a key point is that life may still mean life as being eligible for parole is not a guarantee that any prisoner will be freed.

The Parole Board rules on every case when it is time for a release to be considered. If it believes a criminal should remain behind bars - because they pose a threat to other people, for example - it will not grant
that person's freedom.

Who sets these tariffs?

Judges used to follow guidelines produced by the Court of Appeal, but this was changed by the Criminal Justice Act of 2003.

Now, the Sentencing Guidelines Council produces recommendations for the legal system in England and Wales which it says "encourage consistency in sentencing".

Can judges ignore these guidelines?

The Sentencing Guidelines Council says its recommendations are designed to provide a standard starting point for sentences, but it is then up to the judge to decide how to proceed.

The judge can move significantly away from the guidelines, but must give reasons for doing so.

The defence can always appeal against a sentence felt to be unduly harsh, and equally the prosecution can appeal against a ruling it thinks is unduly lenient.

Lord Falconer told the BBC, however, that the judge in the Sweeney case felt he had to follow the guidelines in the light of a recent Court of Appeal ruling.

Why has this become a political issue?

Home Secretary John Reid criticised Sweeney's sentence for being "unduly lenient".

He is asking Attorney General Lord Goldsmith to consider referring the case to the Court of Appeal, claiming the tariff did not "reflect the seriousness of this crime".

Lord Goldsmith was understood to feel Mr Reid's intervention was "not terribly helpful" because any review would have to be made on legal, rather than political, grounds.

But relatives of the victim welcomed Mr Reid's intervention, having described Sweeney's sentence as "an insult". They called on the government and judiciary to ensure such crimes were "properly punished".

How has the government responded?

The Home Office has promised there will be a "further strengthening" of the rules governing the early release of inmates.

Downing Street has said plans for new legislation will be issued by the time parliament goes into recess for the summer, which happens in less than six weeks. However, it has declined to specify as yet what these laws could be.

What do the Conservatives say?

Leader David Cameron claimed the government played a part in the reduction of Sweeney's sentence by a third, by introducing the Sentencing Guidelines Council in the first place.

He also blamed Labour's Criminal Justice Act for the fact Sweeney would be eligible for parole after five years.

Meanwhile shadow home secretary David Davis has accused the Home Office of "six weeks of serial incompetence" following the recent controversies.

What is the view of the Liberal Democrats?

The party's home affairs spokesman Nick Clegg said public confidence needed to be rebuilt, adding life must mean life when it comes to sentences.

He has suggested renaming the term "life sentence" when it is clearly not for life, with the term only being used in cases where someone is genuinely set to spend their entire life in prison.